Boc-Pro-Hyp-Gly-OBzl and Boc-Ala-Hyp-Gly-OBzl, two repeating triplets found in collagen.

The protected tripeptides benzyl N-{2-[N-(tert-butoxycarbonyl)prolyl]-4-hydroxyprolyl}glycinate or Boc-Pro-Hyp-Gly-OBzl, C24H33N3O7, and benzyl N-{2-[N-(tert-butoxycarbonyl)alanyl]-4-hydroxyprolyl}glycinate or Boc-Ala-Hyp-Gly-OBzl, C22H31N3O7, are the minimum repeating triplets found in collagen. Within the crystal structure of each are two independent peptide molecules with similar structures. The peptides are arranged antiparallel to one another and interact through hydrogen bonds involving the main chains and the 4-hydroxyprolyl groups. The structures exhibit characteristics of a triple helix, but the peptides tend to assume a sheet-like structure.